Figure 6. Bland-Altman plot for measurements of aortic valve annulus diameter obtained with nonenhanced retrospectively ECG-gated multi-detector row CT compared with surgery. Differences are plotted against the mean of the two diameter measurements. Thick solid line represents the mean difference (3.0 mm), thin solid lines represent limits of agreement (range, 0-6.0 mm), and dotted line represents 0. When compared with surgery, nonenhanced imaging allowed overestimation of the diameter by an average of 3.0 mm.